Nut

ABSTRACT

A free spinning nut is formed with an asymmetric, double size recess in its bearing face and flutes in its side faces so as to enhance its holding capacity, particularly when used against softer material.

RELATED APPLICATIONS

This application is a continuation of application Ser. No. 667,051,filed Mar. 15, 1976, and now abandoned, which in turn is a divisional ofmay copending U.S. application Ser. No. 490,463, filed July 22, 1974 nowU.S. Pat. No. 3,989,082 which, in turn, was a continuation of my nowabandoned U.S. application Ser. No. 230,441, filed Feb. 29, 1972 which,in turn, was a continuation of my now abandoned U.S. application Ser.No. 10,940, filed Feb. 12, 1970.

BACKGROUND OF THE INVENTION

U.S. Pat. No. 3,342,236 shows various means for increasing the holdingpower of a free spinning bolt or cap screw, one of which comprises adouble size groove on the bearing face of the bolt head. I havediscovered that a double size groove may also be used to increase theholding power of a free spinning nut in applications where the nut ismade of harder or denser material than the surface against which it isforced and that the holding power and other advantages may beadditionally improved by fluting or weakening the side of the bolt,preferably in alignment with the larger part of the groove.

BRIEF SUMMARY OF THE INVENTION

It is the purpose of my invention to substantially increase the holdingpower of a free spinning nut. This is accomplished by providing anasymmetric groove means in the bearing face of the nut into which willbe forced a slight amount of material of the surface against which thenut is tightened to act as a key inhibiting loosening of the nut.Weakening of the sidewall of the nut by asymmetric flutes or the like toprovide a mass differential provides a further asymmetric condition thatserves to prevent unloosening. The flutes also provide a means toovercome or minimize the end thread loading effect by spreading the loadover several threads, thereby giving a stemming effect.

DESCRIPTION OF THE DRAWINGS

FIG. 1 is a side elevation, partly in section, of a tightened nut andbolt assembly;

FIG. 2 is an enlarged plan view of the nut of FIG. 1;

FIG. 3 is a cross section of the nut of FIG. 1 taken along the line 3--3of FIG. 2;

FIG. 4 is a plan view of a modified form of nut;

FIG. 5 is a plan view of another modified form of nut;

FIG. 6 is a side elevation of either one of the nuts of FIGS. 4 and 5showing the flutes; and

FIG. 7 is a bottom view of another modified form of nut.

DESCRIPTION OF THE INVENTION

Referring to FIG. 1, the two parts 1 and 3 have aligned holes 5 and 7which receive the shank 9 of a bolt 11. The head 13 of the bolt bearsagainst the outer surface 15 of the part 1 and nut 17, which is threadedon the bolt 11, bears against the surface 19 of the part 3. In actualpractice, stress, vibration, and embedding with lapse of time tend tocause the nut and bolt to unscrew from each other with consequent lossof force holding the parts 1 and 3 together and loosening of the joint.It is the purpose of the invention to provide means associated with thenut 17 to resist this tendency of the nut to be involuntarily movedangularly relative to the bolt.

The nut 17 shown in FIGS. 1-3 is symmetrical about a midplaneperpendicular to its axis so that both ends are the same and either canbe used to bear against the surface 19. The nut shown is hexagonal(though it can be any other desired contour) and chamfers 21 blend theends of the nut into the flat sides 23 leaving bearing surfaces 25 thatare circular and concentric on the outer diameter with the axis of thethreaded center aperture 27 of the nut. The inner diameter of eachbearing surface 25 is non-circular and asymmetric by virtue of a grooveor recess 29 surrounding the threaded aperture 27 which has a wide halfsection 31 and a narrow half section 33. The wide section 31 is alsopreferably deeper than the section 33. The wide section 31 is preferablytwice as wide and twice as deep as the narrow section 33. Since theouter part of the bearing surface 25 is circular the stress lines insurface 19 upon tightening of the nut and bolt will flow inwardly intohole 27 instead of outwardly where they might cause a potential fracturecondition.

FIGS. 4 and 6 show a partially modified nut 37 wherein only the bottomof the nut has the bearing surface and the asymmetric recess 29a. Thefour flat sides 23a of the nut which are on the large half 31a of therecess are provided with reliefs in the form of concave indentations orflutes 39 which extend for forming purposes into the top end of the nutand reduce the sidewall thickness of the nut on that half side of thenut. As shown in FIG. 6, the flutes preferably extend more than half butless than the full length of the nut and are shaped as shown in thedrawing. The nut 41 of FIGS. 5 and 6 is similar to nut 37 but the largehalf section 31b terminates in diametral alignment with the corners offlats and the three sides 23b subtended by the section 31b are providedwith the flutes 43. The three flutes 39 preferably reduce the mass ontheir half of the nut 37 by about one-quarter while the four flutes 43preferably reduce the mass on their half of the nut 41 by aboutone-third.

FIG. 7 shows a modified hex nut 45 which has three flutes 47 that extendinto the bearing surface 49 on the bottom face of the nut to form curvednotches 51 in the outer periphery of the bearing surface. In this formthe double width may be omitted (as shown) and the inner periphery ofthe bearing formed as a circle surrounding bolt receiving aperture 53.

By controlling the length and depth of the flutes the number of threadsover which the load is spread when the nut is tightened can be adjustedto eliminate the single end thread loading condition. Thus, the loadcould be spread over two or more threads to give a stemming effect anddistribute the locking action over several threads. Variation of thesize of the flutes also is a means to vary the asymmetric load conditionand off center mass action of the nut to help make the nut highlyresistant to loosening when subject to vibration. The length and depthof the flutes can vary in accordance with the design applications or bestandardized, as desired. The flutes weaken the portion of the threadedwall adjacent them so that it deforms more than the solid, unflutedthread wall and this lets the weakened thread wall portion move in tohold more threads. The amount of such deformation for a given load andnut depends upon the size of the flutes.

The surface 19 of part 3 (and at least a slight depth below it) issofter and/or less dense than the nuts 17, 37, 41, or 45. When the boltand nut are tightened, and/or when set occurs in use, the surfacematerial will flow to some extent into the recess 29, 29a, 29b, or 51where it is trapped. Since the recess 29 varies in width and/or depththe flow-in material will act as a key to resist release or angularmovement of the nut relative to the bolt, i.e., the wider part of thebearing surface cannot track or rotate into the angular position of thenarrow part of the bearing surface. The large section 31 or 49 cannottrack into position occupied by the narrow section 33 or 51 because ofbrinelling action of the nut bearing surface 25 or 49 into the softersurface 19. Embedding of the nut and consequent loss of preload on thebolt 11 will not loosen the joint but instead will increase the lockbecause there will be more flow into the locking recesses. Thedifferential mass in two halves of the sidewalls due to flutes 39, 43,or 47 in nuts 37, 41, or 45 and the asymmetric recess or bearing surfacecondition will create a slight tendency of the nut to cant or bind onthe threads or to store bending energy thereby adding to the lockingaction of the nut.

It is especially significant that the locking action of the present nutdoes not depend upon inserts, thread destruction, or thread deformation.Instead the thread walls are solid and the nut is free spinning off andon and can be reused. In many instances the flow into recesses 29 or 51will be elastic so that there is no substantial surface marring. The useof the counterbore-type recess 29 has the added advantage of eliminatingthe end thread load condition since the end thread is inside theaperture 27. The shape of the nut is such that it can be readily massproduced from conventional metals such as steel, aluminum, etc., as bymanufacture on a five die nut former. It can also be formed ofnon-metallic materials such as "Nylon".

Some modifications of the specific structures illustrated may be madewithin the broad purview of the invention. For example, instead ofinternal threads the apertures 27 could in some applications be smoothand the end of the bolt shank (or stud) peened or swaged over the top ofthe nut to force it against surface 19. Other specific recess shapes forrecess means 29 may be used in conjunction with bearing surface 25 toserve as traps for metal flowing from the softer surface 19 to key thenut in angular position. Other specific side weakening shapes thanflutes 39, 43, or 47 may be used. However, the structures illustratedare presently preferred.

I claim:
 1. A concentric nut that is reusable and substantially freespinning off and on and having an axis comprising a body having an outerperiphery with flats thereon and an inner threaded aperture and anannular flat bearing surface on at least one end face, said outerperiphery, aperture, and bearing surface being substantially coaxial andthe outer periphery being substantially symmetrical in shape withrespect to said axis, said outer periphery having separate individualrecess means of substantial width and depth in each of a plurality ofthe flats on substantially only one axial side of the body to providesaid one axial side with a substantially lesser mass than the otheraxial side so that the mass of the nut is asymmetric with respect tosaid axis to provide for eccentric gripping of several bolt threads whenthe nut is threaded home on a bolt, said recess means terminatingradially outwardly of said aperture and being less than the length ofthe nut and extending into one end face of the nut, the recess meansextending into the bearing surface.
 2. A concentric nut that is reusableand substantially free spinning off and on and having an axis comprisinga body having an outer periphery with flats thereon and an innerthreaded aperture and an annular flat bearing surface on at least oneend face, said outer periphery, aperture, and bearing surface beingsubstantially coaxial and the outer periphery being substantiallysymmetrical in shape with respect to said axis, said outer peripheryhaving separate individual recess means of substantial width and depthin each of a plurality of the flats on substantially only one axial sideof the body to provide said one axial side with a substantially lessermass than the other axial side so that the mass of the nut is asymmetricwith respect to said axis to provide for eccentric gripping of severalbolt threads when the nut is threaded home on a bolt, said recess meansterminating radially outwardly of said aperture and being less than thelength of the nut and extending into said bearing face of the nut, saidnut periphery being hexagonal and said recess means being formed inthree faces thereof.
 3. A nut that is reusable and substantially freespinning off and on comprising a body having a top and an outerperiphery with flat sides and an inner threaded aperture and a flatannular bearing surface, said periphery, aperture, and surface beingconcentric and coaxial, and said periphery having a shape that issubstantially symmetrical with respect to the common axis with thesurface and aperture, said common axis being the axis of rotation of thenut, said bearing surface being normal to said axis, at least one ofsaid flat sides having a concave scalloped indentation thereinterminating radially outwardly of said aperture and extending over morethan half but less than all of the length of the nut and opening intosaid bearing surface and extending over more than half the width of theflat and serving to reduce the thickness of the body between theaperture and the bottom of the indentation as compared with thethickness between the other flats and the aperture and to provide adifferent mass in one half of the body than the other and to spread loadon the nut over more threads than a similar nut not having saidindentation and to provide for eccentric gripping of several boltthreads when the nut is threaded home on a bolt.